android adapter data changed to notify host activity

Question

This is a my use case. I have an activity with a listview and a textview. The textview is the sum of all numbers on the listview, the listview has all the numbers.I have a custom adapter for this case.

On each row of the listview, I have a button. This button will change the number on this row. what I want to do is this:

1. when user clicks the button, the value on each row is changed - doable.
2. the sum on the textview also changes accordingly.

This is a simplified example. In reality, I also have a constraint that I have a data model to represent the data on each role. I am not able to extend the data model to DataSetObserver.

any help?

Answer 1

You should create a listener, which listens for touch on your increment button and inside it call a method of the class extending an interface you created. To make it easy, in your adapter you will have:

public interface OnIncrementListener{
    onNumberIncremented();
}

private OnIncrementListener mListener;

//This is inside getView method of your adapter
myButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            mListener.onNumberIncremented();
        }
});

Then your activity

public class MyActivity extends Activity implements OnIncrementListener {

   //inside onCreate
   myAdapter.setOnIncrementListener(this);
   //end onCreate

    @Override
    public void onNumberIncremented() {
         //Change value of your TextView here
    }
}